1) Field of the Disclosure
The disclosure relates generally to inserts for use in structures, and more particularly, to molded-in inserts for use in composite structures and parts in aircraft, spacecraft, and other vehicles.
2) Description of Related Art
Inserts may be used in the assembly of composite and metal structures or parts for various transport vehicles, such as aircraft, spacecraft, rotorcraft, watercraft, automobiles, trucks, buses, or other transport vehicles. Such inserts may be used to receive mating fasteners, provide attachment points for multi-part assemblies, and provide load transfer points. Examples of such inserts may include press-fit inserts, swaged inserts, molded-in inserts, threaded inserts, or other suitable inserts or fittings.
Methods for installing inserts into composite and metal structures or parts may include, for example, mold in place methods, such as where molded-in inserts are installed during molding, or for example, more expensive post-molding methods, such as where press-fit inserts or swaged inserts are installed after molding.
Known press-fit inserts and swaged inserts may be pressed into an opening in metal structures or parts after molding without the use of special tools or fasteners. However, known press-fit inserts and swaged inserts designed for press-fit installation in metal structures or parts may not work well with fiber reinforced thermoplastic composite structures or parts due to the non-ductile nature of the fiber reinforced thermoplastic composite material. Such non-ductile fiber reinforced thermoplastic composite material may lead to over-stressing of the material around the insert if the fit is too tight or may lead to poor retention of the insert if the fit is too loose, thus resulting in an improper fit. Thus, a proper fit of such known press-fit and swaged inserts may be difficult to attain with non-ductile materials such as fiber reinforced thermoplastic composite material. Moreover, post-molding methods for installing known press-fit inserts or swaged inserts may incur increased labor and manufacturing costs, increased set-up and operating time, and increased final part cost.
Known molded-in inserts and threaded inserts may be molded into the composite or metal structure or part during molding. For example, FIG. 2A is an illustration of a front perspective view of a known molded-in insert 30 that may be molded in place in injection molded structures or parts. The molded-in insert 30 has knurled surfaces 34 with sharp knurls 36 and has a groove 38 with sharp edges 40, sharp internal corners 42, and a small width 44. Further, FIG. 2B is an illustration of a front perspective view of a known molded-in threaded insert 32 that may be molded in place in injection molded structures or parts. The molded-in threaded insert 32 has knurled surfaces 34 with sharp knurls 36, has groove 38 with sharp edges 40 and sharp internal corners 42, and small width 44, and has internal threads 46. Such known molded-in insert 30 and molded-in threaded insert 32 may use the knurled surfaces 34 and/or grooves 38 with sharp edges 40, sharp internal corners 42, and small internal radii 44 to retain such molded-in insert 30 and molded-in threaded insert 32 in place in thermoplastic composite parts.
However, such known molded-in insert 30 and molded-in threaded insert 32 may not work well with compression molded fiber reinforced thermoplastic composite structures or parts due to difficulties in filling the small radii 44 or the sharp internal corners 42 of the groove 38 during the molding process. FIG. 3 is an illustration of a cross-sectional top view of the known molded-in insert 30 showing the knurled surface 34 with sharp knurls 36 after being compression molded in place in a carbon fiber reinforced thermoplastic composite part 50 comprised of a carbon fiber reinforced thermoplastic composite material 52 having reinforcing carbon fibers 54 in a resin matrix 55. The reinforcing carbon fibers 54, in general, do not flow into or enter void areas 56 between the knurls 36, and thus, the formation of such void areas 56 of incomplete consolidation may be promoted within the carbon fiber reinforced thermoplastic composite material 52, which can undermine retention strength of the molded-in insert 30 within the carbon fiber reinforced thermoplastic composite part 50. Moreover, the reinforcing carbon fibers 54 of the carbon fiber reinforced thermoplastic composite material 52 may not flow into the small radii 44 (see FIGS. 2A, 2B) and/or sharp internal corners 42 (see FIGS. 2A, 2B) and may thus limit retention strength to the capability of the resin matrix 55 alone, which may be relatively weak.
Further, such known molded-in insert 30 and molded-in threaded insert 32 may have sharp edges 40 (see FIG. 4) which may cut reinforcing carbon fibers 54 during the molding process. FIG. 4 is an illustration of a cross-sectional side view of known molded-in insert 30 showing the groove 38 with sharp edges 40 and sharp internal corners 42 molded in place in the carbon fiber reinforced thermoplastic composite part 50 comprised of carbon fiber reinforced thermoplastic composite material 52 having reinforcing carbon fibers 54 in a resin matrix 55. The pressures on and flow of the carbon fiber reinforced thermoplastic composite material 52 during molding may cause the reinforcing carbon fibers 54 to have difficulty flowing into the sharp internal corners 42, thus creating void areas 56 of incomplete consolidation. Pressures on and flow of the carbon fiber reinforced thermoplastic composite material 52 during molding may cause the reinforcing carbon fibers 54 to be cut or severed when pressed against the sharp edges 40, such as at locations 58. Cut or severed reinforcing carbon fibers 54 may undermine retention strength of the molded-in insert 30 within the carbon fiber reinforced thermoplastic composite part 50.
FIG. 5A is an illustration of a cross-sectional side view showing void areas 56 of incomplete consolidation where reinforcing carbon fibers 54 of carbon fiber reinforced thermoplastic composite material 52 are forced to flow around a relatively sharp edge 60 of a carbon fiber reinforced thermoplastic composite part 62. FIG. 5B is an illustration of a close-up view of the circled portion 5B of FIG. 5A showing the void areas 56 of incomplete consolidation. Such void areas 56 of incomplete consolidation may undermine retention strength of molded-in inserts within the fiber reinforced thermoplastic composite parts or structures.
Accordingly, there is a need in the art for a molded-in insert and method for high strength retention in fiber reinforced thermoplastic composite parts or structures that provide advantages over known devices and methods.